Function Help

I am brand new to C++, I decided to start learning it because I have always had an interest in programming and now that my BS is done I have some spare time. I am having some trouble with functions and have been beating my head against the wall for a few days trying to figure out where I am making my mistakes. I completely understand the purpose of functions I just can't seem to grasp how to use them properly.

This program is a really basic program just to test my use of functions. It has a calculator, and a loop which sings 99 bottles of beer. I've looked through a bunch of different books, websites, and forums, and as far as I can tell it feels like I am doing the functions right, but apparently I am not because I can't get this to compile.

Any advice anyone could give would be greatly appreciated. Thanks in advance!